NMR studies of the partially disordered state in a triangular antiferromagnet UNi4B

A. Oyamada, M. Kondo, K. Fukuoka, T. Itou, S. Maegawa, Tokushin Ri, Y. Haga

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11 Citations (Scopus)

Abstract

A triangular antiferromagnet UNi4B experiences a partially disordered state, in which two-thirds of U 5f moments order in a vertex-like structure and one-third of U 5f moments remain paramagnetic. Magnetization and NMR measurements of UNi4B have been performed to study the dynamical properties of U magnetic moments in the partially disordered state. The value of the effective moment above TN derived from the fitting of the Curie-Weiss law suggests a significant crystal field splitting and the Kondo effect. The Weiss temperature was also estimated to be -28K, which suggests that the exchange interaction is antiferromagnetic. Furthermore, the exchange interaction estimated from the relaxation rate T1-1 above 50K is 18K, which is close to the Weiss temperature. These results suggest that the dominant interactions between U moments are antiferromagnetic in the basal plane. The relaxation rate T1-1 decreases abruptly below TN down to 15K and is almost constant between10 and 15K. In the same temperature range, the magnetic susceptibility still increases with decreasing temperature. However, the effective moment estimated below TN is almost the same as that above TN. This shows that there are anomalous fluctuations below TN which cannot be explained by the simple model.

Original languageEnglish
Article number145246
JournalJournal of Physics Condensed Matter
Volume19
Issue number14
DOIs
Publication statusPublished - 2007 Apr 11

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics

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